Release v16.1.0

Changed

• Fluent projection accessors that are not a simple member access (string interpolation, arithmetic, method calls, constants, or expressions that ignore the parameter such as _ => DateTimeOffset.UtcNow) now throw a descriptive InvalidPropertyExpression at definition time instead of silently mapping to nothing. This applies across the whole fluent projection surface — value/key accessors and target-property selectors. A projection that relied on such an accessor was already projecting nothing; it now fails loud at registration.

Fixed

• Observable read-model queries (ObserveById / ObserveSingle / live queries) now decrypt [PII] values when the projected document carries no explicit __subject, resolving the compliance subject the same way one-shot queries do.
• ReadModelScenario<T> now backfills a [Join] value regardless of seed order, for both root-level and child-collection joins and any key type.